1. Field
One or more embodiments of the present disclosure relate to a small-sized projector for projecting an image on a screen.
2. Related Art
Recently, technology developments related to a small-sized projector which projects externally and displays data or moving pictures stored in a display apparatus, such as a mobile phone, a computer, an MP3 player, and a small-sized digital camera, as images, have been rapidly made. Generally, a small-sized projector has a small-sized flat-panel-type display device such as a digital micro-mirror device (DMD) or a liquid crystal display (LCD).
Also, a projector generally has an illumination optical system and a projection optical system.
The illumination optical system denotes an optical system arranged in an optical path from a light source to a display device, and the projection optical system denotes an optical system arranged in an optical path from the display device to an external screen.
In order to install a projector in a small-sized display apparatus, the required size of a projector has been gradually decreasing. However, if the projector is made small enough to be installed in a small-sized display apparatus, optical devices of the illumination optical system and the projection optical system may interfere with each other. For example, when an optical device forming an illumination optical system is placed in an optical path of a projection optical system, light reflected from the optical device may be incident on the projection optical system to form a ghost image. To prevent this, a method for multilayer thin-film evaporation to prevent reflection on the surface of the optical device is used. However, this method reduces production speed of the optical device and may degrade contrast ratio or color gamut and thus degrade the quality of images.